Introduction

Postoperative sore throat (POST) is a common complication. The incidence of POST varies between 18% and 65% and lasts for 12-24 hours after surgery (1,2). It is caused by local tissue trauma and pharyngeal mucosal inflammation (2). The risk factors of POST include head and neck surgery, female gender, nausea and vomiting, cuff pressure and difficult intubation (3). POST affects the healing process by negatively affecting the nutrition and fluid intake of the patients. On the other hand, reducing postoperative complications reduces the length of hospital stay and increases patient satisfaction (4,5).

Due to the extensive etiologies of POST, several methods are used to prevent and reduce it. These methods usually include pharmacological (1,3) and clinical applications. Some of the clinical applications include acupuncture, cuff pressure, difficult intubation interventions, soaking the endotracheal tube (ET) with water-soluble gel, and nerve block (6-9). However, the routine use of these applications is limited, and there is no clinical standard (10).

Postoperative pain control includes nursing interventions as well as pharmacological and clinical applications. Hot and cold applications such as cold vapor (4,11), licorice (2) and luo han guo (12) are among the nursing interventions. These limited studies are novel and include easy-to-apply nursing interventions for the prevention and reduction of POST (2,4,11,12). However, a systematic review calculating the effect size of these interventions has not been found in the literature.

Methods

Aim

To determine and compare non-pharmacologic methods in managing POST in adult patients undergoing endotracheal intubation.

Design

The research question is “What is the effect of non-pharmacological methods in managing sore throat as a result of a postoperative endotracheal intubation?” This research complied with the principles of the Cochrane Guideline (13) and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Two independent researchers (HO, TY) reviewed the titles and abstracts of the studies according to the inclusion criteria (Figure 1). The researchers (HO, TY) analyzed the data one by one. At all stages, discrepancies were resolved through consensus and collaboration of the researchers (HO, TY).

Inclusion and Exclusion Criteria

Inclusion Criteria

Experimental studies meeting the PICOS criteria were included in the study:

Patients: Adult patients undergoing intraoperative endotracheal intubation and elective surgery.

Intervention: Non-pharmacological interventions in POST management.

Comparison: Intervention and control group.

Outcome: POST.

Study design: Only full-text English articles that contain experimental research published between 2010 and 2022 were included in this review.

Exclusion Criteria

Congress abstracts without full-text articles,

Editorial letters,

Non-English articles,

Studies with pediatric patients,

Pharmacological studies,

Other clinical studies (acupuncture, cuff pressure measurement, difficult intubation interventions, nerve blocking).

Definition of Outcome Measures

The outcomes of the study were the severity and incidence of postoperative sore throat. These outcomes were evaluated in the postoperative care unit (PACU) between the first 24 hours and the third day after surgery.

Literature Search Strategy

PubMed, Scopus, MEDLINE, Web of Science and EBSCOhost databases were used in this study. The databases were searched between January 1, 2010 and February 1, 2022, with no restrictions on article status (abstract or full text, etc.). Search terms included “sore throat”, “endotracheal intubation”, “postoperative complication” and “hoarseness”. The search was performed by combining indexed (e.g. MESH) and free text (sore throat* OR postoperative sore throat) terms using “AND” as follows: (endotracheal intubation) AND (postoperative complication* OR hoarseness). The study followed the PRISMA guideline recommendations (14).

Study Selection

A total of 857 articles were found in the initial review. After eliminating duplicates and non-English language studies, the number of studies selected for the final survey was 338. The abstracts of these articles were reviewed for exclusion criteria. After excluding letters to the editor (n=1), pharmacological (n=237) and pediatric studies (n=35), the remaining 65 articles were subjected to an additional full-text evaluation to decide which articles to use. Finally, 58 articles about clinical practice were excluded and seven articles about nursing intervention were included (Figure 1).

Data Extraction and Analysis

Two reviewers (HO, TY) independently extracted data from the included studies using a pre-designed data extraction form. The extracted data included study design, study location(s), sample size, patient characteristics, the measurement tool used to assess the severity of sore throat, and the effect of the non-pharmacologic method on POST (Table 1).

Quality Appraisal

This review used the Cochrane tool for assessing risk of bias (RoB) in randomized trials (15), which consists of five domains: Randomization process, Deviations from intended interventions, Missing outcome data, Measurement of outcome, and Selection of reported outcome. Table 2 summarizes the results of the RoB assessments.

Results

Study Characteristics

Two of these studies were conducted in Turkey (4,11) two in China (10,12) one in Austria (2) and two in Korea (16,17). One of these studies was quasi-experimental (11), one was single-blind, and five were double-blind randomized controlled studies.

Characteristics of the Patients

The total number of patients in all studies was 1.092. However, 1.067 patients were included in the study sample since 14 patients from the study of Tan et al. (12) and 11 patients from the study of Yu et al. (18) dropped out after the initial selection.

Regarding the sociodemographic characteristics of the participants, the mean age of the patients was 51.37±13.84 years and the mean body mass index was 25.59±5.12 kg/m². Most of the patients in the studies were female. Inclusion criteria were similar among the included studies: The patients were over the age of 18, planned for elective surgery under general anesthesia, without preoperative sore throat and hoarseness, had ASA scores I-II (2,4,10,17), had Mallampati Score I-II (4), had Body Mass Index <30 kg/m² (16), had Cormack-Lehane Grade I-II (12). The included patients underwent general surgery, lumbar disc herniation, hysterectomy, thoracic surgery and nasal surgery.

Exclusion criteria included difficult intubation or multiple intubation history (2,11,12), steroid drug therapy (10-12), difficulty in co-operation, chronic respiratory system disease (2,11,12,17), psychiatric diagnosis, ASA score ≥III, Mallampati score ≥II-III, presence of nasogastric catheter (4,12), head and neck surgery history, operation time <30 min (4,10,17), a surgery history within last month (2), BMI >40 kg/m², nonsteroidal anti-inflammatory drug use within last 24 hours (2,10), and having cervical spine diseases (17).

Control of Sore Throat

Table 1 shows the details of interventions for sore throat due to intubation in the studies. In these studies, the interventions administered to patients in the intervention group for the management of sore throat were cold vapor-ice cube cold vapor, oxygen administration with cold vapor, licorice extract, luo han guo and thermal softening of ET (2,4,11,12,16,17). As for control groups, three studies had no-intervention control groups (4,10,11), one study applied a placebo with licorice-like taste (2), one study applied black tea (12), and two studies kept the ET at operating room temperature (16,17).

The severity of POST was assessed using scales such as Visual Analog Scale, Numerical Rating Scale and subjective questions (none, mild, moderate, severe). Pain levels were assessed at 2, 4, 6, 12, 24 hours and 3 days postoperatively at the postoperative recovery unit. The results showed that “cold vapor” and “cold vapor-oxygen combination” were not statistically significantly effective in reducing sore throat (11). “Cold vapor-ice cubes-cold vapor combination” and “ice cubes” application were not effective in reducing the severity of sore throat at zero and second hours after surgery, but were effective at 6^th and 24^th hours (4). While licorice reduced the severity of sore throat 30 minutes, 1.5 hours and 4 hours after surgery (2), luo han guo was found to reduce the severity at the 12^th, 24^th and 48^th hours after surgery (12). Furthermore, thermal softening of ET significantly reduced the incidence of POST (16,17).

Discussion

Intubation tubes are commonly used to maintain breathing in patients undergoing surgery under general anesthesia. However, difficult intubation can cause airway damage. Moreover, ET cuff pressure is an important factor in mucosal irritation and inflammation. Therefore, different postoperative complications associated with ET are common. POST is one of these complications (2,16,19,20). It has been reported that the frequency of POST peaks between the 2^nd and 6^th hours after extubation and decreases over time (21,22). Although pain management in postoperative period is among nursing interventions, studies are inadequate. There are different practices in POST management. These practices generally aim to reduce tissue trauma and prevent inflammation during intubation (2,4,16,17).

Thermal softening of the ET allows the ET to form easily and thus reduces physical trauma to the larynx. Seo et al. (17) used saline heated at 40 °C and a softened intubation tube for the patients undergoing elective thoracic surgery. They observed that the incidence of POST was significantly reduced by 20% on the first day. Yu et al. (18) similarly found that thermal softening of ET reduced the incidence and severity of sore throat in the first hour after surgery. These findings show that thermal softening is a simple and easily applied method in POST. Wang et al. (10) used chewing gums to reduce physical trauma for the management of POST and found that sore throat decreased at the 2^nd, 6^th, and 24^th post-operative hours. Chewing gum increases salivation and reduces intubation-related trauma by lubricating the oral cavity (10). The results suggest that thermal softening of ETs and the use of chewing gum may be among the nursing interventions to reduce POST with an interdisciplinary approach.

Hot and cold applications reduce inflammation in patients undergoing endotracheal intubation. Herbal teas are presented as hot applications in the literature. Licorice was used in this systematic review and meta-analysis (23). The researchers used herbal teas prophylactically and reported that herbal teas significantly reduced sore throat within 30 minutes, 1 hour and 4 hours postoperatively. Licorice contains glycyrrhizin and has anti-inflammatory and antiallergic effects. Glycyrrhizin reduces prostaglandin secretion and inhibits inflammation by slowing platelet aggression (24,25). Tan et al. (12) used luo han guo to reduce POST and observed that sore throat was reduced in the 12^th, 24^th and 48^th postoperative hours. Luo han guo is an anti-inflammatory, antibacterial herb widely used in Traditional Chinese Medicine to moisturize the lungs, relieve heat and alleviate cough (26,27). These findings suggest that anti-inflammatory herbal teas can be cost-effective applications in nursing interventions to reduce POST. However, the correct use of herbs may require further knowledge. Therefore, integrative applications are recommended.

Cold applications affect POST by reducing the capillary permeability, controlling edema, reducing the risk of hematoma formation and bacterial activity, preventing the transfer of pain stimulus to the upper centers, and eliminating painful spasms (28). It is observed that “cold vapor” and “ice cube” applications are used to cope with POST (4,11). In the literature, it has been reported that cold vapor can relieve complications such as hoarseness, cough, dry throat and sore throat due to laryngeal damage (29-33). Sahbaz and Khorshid (4) also suggested that cold vapor application, which was easy to apply, had no side effects and low drying cost, might reduce sore throat in the first hours after surgery. However, some studies showed that the effect of cold applications (such as cold vapor and ice cubes) in managing POST was not statistically significant.

Bulut et al. (11), applied cold vapor to the patients in the intervention group for 15 minutes in the first hour after admission to the PACU, while no intervention was applied to the patients in the control group. No statistically significant difference was found between the incidence of sore throat in the intervention and control group patients at the 2^nd, 4^th, 8^th and 24^th hours. Similarly, in the study of Özsoy et al. (34), cold vapor was applied to the patients in the intervention group at 0, 2 and 6 hours after surgery. No intervention was applied to the control group. As a result, no statistical difference was found between the POST levels of the patients in the intervention and control groups. Özsoy et al. (34), attributed the similarity between the two groups to the short operation time, successful intubation placement in the first attempt, appropriate ET use and postoperative analgesic doses (34). The time of starting oral intake, frequency of cold application, duration of application and cuff pressure within the normal range may affect the difference between the groups in cold applications.

Study Limitations

This systematic review had several limitations. It included only English-language experimental studies and addressed only the adult patient group. Furthermore, this review was not recorded and published in a specific protocol due to time constraints and limited resources.

Conclusion

POST is a common complication in adult patients undergoing elective surgery. However, interventions mainly include pharmacological and other clinical interventions (acupuncture, cuff pressure, difficult intubation methods, etc.). Nursing interventions with thermal softening, chewing gum and herbal teas significantly reduce POST. However, cold applications that prevent inflammation (cold vapor, etc.) provide only an insignificant decrease in the severity of POST. There are limited number of studies on nursing interventions and more randomized controlled trials are needed.

Ethics

Peer-review: Externally peer reviewed.

Authorship Contributions

Surgical and Medical Practices: H.Ö., T.Y., Concept: H.Ö., T.Y., Design: H.Ö., T.Y., Data Collection or Processing: H.Ö., T.Y., Analysis or Interpretation: H.Ö., T.Y., Literature Search: H.Ö., T.Y., Writing: H.Ö., T.Y.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.